Michael Fassbender, the 34-year-old Irish actor, is having a banner year. Cast in several of the biggest critical hits of 2011 and this year’s winner of the prestigious Best Actor Award at the Venice Film Festival, he’s already become one of the world’s great leading men.

But 2012 is looking like the year in which he achieves complete global dominance, and his fans couldn’t be happier about it. Fassbender is that rare thing after all, a combination of brooding good looks and a genuinely once in a generation acting talent.

In A Dangerous Method, the absorbing new David Cronenberg film opening this Friday about a bitter conflict between two of the titans of the 20th century, Carl Jung and Sigmund Freud, Fassbender stars in a dark tale of sexual and intellectual discovery that’s based on true-life events.

When fledgling psychiatrist Carl Jung (Fassbender) and his mentor Sigmund Freud (Viggo Mortensen) encounter the troubled young Russian woman Sabina Spielrein (Keira Knightley), the beautiful young woman quickly comes between them. Into this already combustible mix comes Otto Gross, a debauched and amoral young patient who appears to have no sexual or social boundaries at all.

A Dangerous Method (the title refers to the act of psychoanalysis itself, which was considered dangerous by Sigmund Freud’s critics) is based on Academy Award winning writer Christopher Hampton’s original play, The Talking Cure. Hampton already has two classic screenplays like Dangerous Liaisons and Atonement under his belt, so his script for the new film is as absorbing as you’d expect.

Fassbender in particular is a revelation in a performance that simply outshines every other actor on the screen. It’s because he’s in possession of that all too rare gift -- the ability to completely convince you he actually is the character he’s playing.

He’s so good, in fact, that he carries this brooding, anxios and overlong film on his own back all the way to the closing title.

Which is not to say that A Dangerous Method is a dull film. In fact it’s central ideas are completely fascinating, and it has interesting and provocative things to say about marriage, sexuality, love and commitment (which are all evergreen subjects, after all).

But it’s the way that we get to these interesting discussions that rankles a bit. First of all there’s the musical score by Lord of the Rings composer Howard Shore.

With its orchestral strings blaring out from the opening shot, it seems to be telegraphing to us that this is a classy, serious film. Unfortunately the music contrasts sharply with the at times quite unhinged performance of Knightley, who early on looks mostly bewildered and bewilderingly miscast.

Knightley elongates her jaw impressively in the opening scenes to indicate she’s having serious mental problems, but she’s so absurdly pretty -- even in extreme situations -- that you already know things are going to work out for her eventually.

Even when she takes an unscheduled dip in the sanatorium pool, she manages never to let the mud cover her gorgeous auburn tresses. It’s as if, mad and all as she is, she was smart enough to hire a stylist and a costume designer to ensure she never looks too loopy.

Knightley can act, but she’s out of her depth as the curiously seductive young Russian Jew the script needs her to be. It’s only when Fassbender appears that the film achieves a genuine dramatic intensity, and it’s all thanks to his remarkable skill as an actor.

In the film Fassbender plays Jung just as he’s starting out on his world changing career and making use of Freud’s experimental treatment known as psychoanalysis, or the talking cure. Early on he meets 18-year-old Sabina Spielrein, who has been diagnosed with hysteria and is given to violent fits and outbursts.

You can see what’s coming a mile off, but the film slowly reveals that Spielrein has been abused by her authoritarian father, who subjected her to repeated beatings and humiliations during her childhood. The connection between emotional disorders and sexuality confirm Freud’s theories and make an early convert out of Jung when it comes to his method.

That discovery leads to a friendship forming between Jung and Freud, who begins to see the young man as his intellectual heir.

But then another charismatic young patient enters Jung’s life in the form of Otto Gross, a drug addict who is committed to his own sexual gratification. He skillfully argues against Jung’s commitment to monogamy, pushing the boundaries and ethics of the man who is supposed to be curing him.

It’s a remarkable sequence, and Fassbender is superb as he struggles with his professional commitments, his marriage and his basic and longstanding desire to make love to Spielrein.

Eventually he pushes aside his qualms and begins a heady affair with his former -- but now cured -- patient. It’s a move that violates the doctor/patient relationship, and it leads to an ethical clash between Jung and his far more patrician college Freud.

The fight between the two learned men, which hinges ultimately on Freud’s inability to ever allow his former student to become his colleague (his equal, in other words) eventually leads to a complete break between the two men, and a rupture in psychoanalysis that would endure for decades.

But oddly enough, it’s in the chemistry and the philosophical battles between Fassbender and Mortensen that A Dangerous Method really comes to life.

In their own time both men were conscious that their groundbreaking work would be profoundly influential, and they both wanted to guard its legacy and ensure it could continue. That passion led to a rigidity of mind in Freud that Jung rebelled against, over and over.

But Jung too had his blind spots. In the beginning he was bourgeois and conventional in his outlook, a product of his class and period, and he refused to acknowledge that some of the hostility to Freud’s talking cure method had its origins in hostility to Freud’s ethic background (the Nazis eventually drove him out of Europe).

The action of A Dangerous Method is taken directly between the correspondence between Jung, Freud and Spielrein and so it achieves its sense of authenticity directly from the source.

But Fassbender’s turn as the tortured and blazingly brilliant young Jung is the greatest part of the film. He plumbs the emotional core of his character in a way that surpasses his co-stars, and in the process he saves this slow moving but still quietly compelling film from becoming a biopic about a titan of the 20th century.

It’s not giving too much away to say that the ending is as bittersweet as we begin to anticipate early on. The collusion of personalities, theories, desires and broken hearts make it a dead cert almost from the beginning.

It’s Fassbender’s all-electric performance that will be remembered. He’s already the kind of actor that simply can’t fail.